Because the white plastic can make it difficult to see the milled numbers for the leadholders, I have begun coloring the numbers. The one is red and the rest are blue, to make them easier to see quickly. 
I have also upgraded the lead holders again as a few customers had difficulty with the thinnest leads sliding back into the holder.
Following on the success of the MG402 case, Micro-Metrics has added a similar case for the H-501 Pencil Hardness Gage.
The H-501 Pencil Hardness Gauge now comes in a polypropylene carrying case complete with the testing device, fourteen leads in a carrying case, a dressing disk with four replacement adhesive sandpaper disks, and a technical data sheet.
If you wish to replace your old-style vinylette case, please contact Micro-Metrics or your favorite distributor to purchase a replacement. The new case costs $34.00 (plus shipping).
(Shown, above, with a red pen, not included, to demonstrate use of the pen slot.)
The new case has a cut-out to carry a pen. Because everyone seems to want a different kind of pen (indelible pen, erasable marker, pencil, grease pen), no pen is included in the case: pick your favorite!
Having heard that the lead holders occasionally break in use, I’ve replaced the part-metal and part-plastic lead holders with all-metal lead holders. These have proven to be durable.
The stack-of-five sandpaper discs used with the H-501 dressing disk (part number H-501-20) is now replaced by a higher quality “single disk at a time” version using a better adhesive. The disc kit fits into the H-501 carry case, so you will always have spares on hand when you need them.
You can now purchase replacement disc kits (five sandpaper discs, without the plastic disk they mount on) instead of having to replace the entire dressing disk. Disc kits (part number H-501-20R) sell for just $11.
The plastic disks (H-501-20) are, of course, still available; and they come with the five sandpaper discs.
LED bulbs
At long last, I have found a direct source for the #222 LED bulbs, so Micro-Metrics is able to lower the price of the LED bulb to $1.80.
Upgraded H-501 Pencil Hardness Gauge
The H-501 Pencil Hardness Gauge has been upgraded. In place of the previous gray plastic body, the H-501 (and the dressing disk base) are now made using a higher-quality white plastic. The lead holders now come with all-metal barrels, instead of the older version that was part metal and part plastic.
Technical Data Sheets
There is a new webpage on the Micro-Metrics website with links to the Technical data sheets that come with Micro-Metrics products as PDFs in printable form. (I have reformatted them so they can be printed on 8-1/2″ by 11″ paper.) There is also a white paper entitled: “Measuring: the Geometry of the Tooke Gauge.” (A customer requested a TDS on how to replace the lightbulb, which is also there now.)